I was at the Harford Co Compost facility last week. You show your driver's license at the gate. County residents can haul away a certain amount of compost or mulch for free. As you noted, larger amounts are sold for a charge.
The compost is black and completely decomposed. Best of all, no weed seeds like manure. If I were you I would get a truckload, just come down Conowingo Road and right onto Sandy Hook Rd., hang another right at the 3-way stop.
Even better, you can haul brush, grass, leaves etc down and get rid of it on the same trip. Be sure to bring a tarp or it will all blow out on your way home.
Sam